(a) Field of the Invention
The present invention relates to an optical information recording medium used suitably in recording and regenerating information with a laser beam, said medium being provided with a recording layer containing a cyanine dye in which a halogen atom is present in at least one of each 4, 6 and 7-positions of its indole and indolenine rings.
(b) Description of the Prior Art
A method of recording and regenerating information by radiating a laser beam on a rotating disk-shaped optical information recording medium has hitherto been known. As the optical information recording medium for use in this method there has been proposed the one which comprises providing, on a substrate, a thin layer of a low melting metal or a mixed thin layer of this metal and a dielectric substance.
However, the optical information recording medium of this sort is disadvantageous in respect of inferior preservability, low resolving power, low recording density, high production cost and the like. In view of this, it has recently been proposed to use an organic dye thin film, whose physical properties are changeable upon exposure to a relatively long wavelength light such as a semi-conductor laser beam, as a recording layer. However, the dye thin film having absorptivity on the long wavelength side involves the problems that it is generally inferior in stability against heat and light (inclusive of regenerating light after completion of recording) and the like. Accordingly, the fact is that a recording layer having satisfactory recording characteristics has not been developed yet.